Meowey, I had a daughter that tried the vegan thing once (missed my grilled steaks). For a stuffed bell pepper for her I grilled a portabella mushroom and some sliced sweet onions (that had been brushed with some EVOO -extra virgin olive oil-)
'til they were nice and tender. These were then given a coarse chop and added to some left over Corn bread stuffing. The mixture was stuffed into a bell pepper and some 'mater juice poured over the top and cheese place on top of that. This was baked at 350* until the pepper was nice and tender and the stuffing was good and hot (above 140*).